Analog Devices Inc. LTC5544IUF#PBF

Overview

LTC5544IUF#PBF from Analog Devices (acquired Linear Technology) is a high-dynamic-range passive downconverting mixer optimized for 4GHz–6GHz RF input and 4.2GHz–5.8GHz LO operation. It delivers 7.4dB conversion gain, 25.9dBm IIP3, and 11.3dB noise figure at 5250MHz with 2dBm LO drive, targeting WiMAX/WLAN receiver front-ends requiring wide IF bandwidth up to 1GHz.

For engineers reviewing the LTC5544IUF#PBF datasheet, LTC5544IUF#PBF pinout, LTC5544IUF#PBF application, or LTC5544IUF#PBF equivalent, key selection criteria include its dual-supply IF amplifier (3.3V/5V), shutdown control, temperature sensing diode, and QFN-16 package thermal performance in demanding 5GHz public safety and military comms systems.

Technical Context

The LTC5544IUF#PBF integrates a passive double-balanced mixer core, LO buffer amplifier, IF differential amplifier, and bias/shutdown circuitry. Its RF and LO inputs are single-ended with 50Ω matching; IF output is differential open-collector with adjustable bias via IFBIAS and LOBIAS pins.

It supports both low-side and high-side LO injection, with LO-to-RF isolation >38dB and LO-to-IF isolation >21dB. The internal transformer-based RF/LO interface enables broadband matching while maintaining high linearity across 4–6GHz, validated by measured S11 < –12dB over full RF range when LO is driven.

Key Specifications

Pinout & Package

Package: 16-lead (4mm × 4mm) plastic QFN with exposed thermal pad (Pin 17 = GND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-frequency downconverting mixer applications.

Compared with HMC1040LP4E and ADL5802ACPZ-R7, the LTC5544IUF#PBF uniquely combines 4–6GHz RF operation, integrated IF amplifier with dual-supply flexibility, and on-chip temperature sensing-enabling compact, thermally aware 5GHz receiver designs without external signal conditioning.

Availability

LTC5544IUF#PBF is available at Aetrix Electronics and suitable for 5GHz WiMAX/WLAN receivers, 4.9GHz public safety radios, and military communications systems requiring stable component supply across extended temperature ranges.

Supply support for LTC5544IUF#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017 and maintains its high-performance RF product lines with rigorous qualification standards.

The LTC5544IUF#PBF belongs to Linear's high-dynamic-range passive mixer family, designed specifically for wideband receiver front-ends in wireless infrastructure, defense, and test equipment where linearity, noise, and thermal stability are critical.

FAQ

What is the recommended LO drive level for optimal performance of the LTC5544IUF#PBF?

The LTC5544IUF#PBF achieves best-in-class IIP3 and noise figure with a nominal +2dBm LO drive across its 4.2–5.8GHz range. Performance remains excellent within ±3dB (–1dBm to +5dBm); however, LO power exceeding +5dBm may degrade linearity slightly. The datasheet specifies +2dBm as the reference condition for all AC electrical characteristics including the 25.9dBm IIP3 at 5250MHz.

Can the LTC5544IUF#PBF operate with a single 3.3V supply for both mixer and IF amplifier sections?

Yes, the LTC5544IUF#PBF supports single-rail operation: VCC1/VCC2 and VCCIF can all be tied to 3.3V. In this configuration, the IF amplifier draws 98mA and delivers 11.4dBm input P1dB at 5250MHz. For higher linearity, VCCIF may be increased to 5V independently, raising P1dB to 14.6dBm while increasing total supply current by only ~3mA.

How does the shutdown function work on the LTC5544IUF#PBF, and what is its impact on power consumption?

The LTC5544IUF#PBF uses active-low shutdown: SHDN < 0.3V enables normal operation (~194mA total current), while SHDN > 3.0V disables the device, reducing supply current to 500µA. Turn-on and turn-off times are both 0.6µs, making it suitable for fast TDD switching. The SHDN pin must not float and draws <30µA, allowing direct interface with standard CMOS logic.

What is the purpose of the CT (Pin 3) and how should it be used in the LTC5544IUF#PBF layout?

CT (Pin 3) connects to the center-tap of the internal RF transformer secondary. It enables insertion of a bypass capacitor (C2) to suppress LO-to-RF leakage-critical for meeting spectral mask requirements. Recommended C2 values range from 0.4pF to 1pF depending on LO frequency; the capacitor must be placed within 2mm of Pin 3 for effective HF decoupling. Nominal DC voltage at CT is 1.2V, requiring DC isolation from ground and VCC.

Does the LTC5544IUF#PBF support both low-side and high-side LO injection, and what are the performance trade-offs?

Yes, the LTC5544IUF#PBF supports both configurations. Low-side LO (fLO = fRF – fIF) yields 7.4dB gain and 25.9dBm IIP3 at 5250MHz; high-side LO (fLO = fRF + fIF) gives 7.3dB gain and 24.0dBm IIP3 at same frequency. High-side operation shifts image rejection requirements and may improve LO leakage in certain layouts, but trades ~2dB IIP3. Both modes maintain >29dB RF-to-IF isolation and require identical external matching networks.